My charger would only charge for a little more than 5 minutes when it thought my battery was full. Apparently that is it's built in time limit. However, my battery was NOT full initially, even though the Pronto and subsequently the charger thought it was. It took a reboot, a reseat and a swear word or two to get it working fine. The Flashing, I'll assume is a warning message. It could be that since your battery is full it actually is getting a slight overcharge in that 5 minutes and signaling the error. Try NOT charging it for a few day, until you can see the battery meter showing 3/4 or 1/2 full. The charger should then charge for more than 5 minutes, and it may be better able to prevent an overcharge error. Just a thought. Hope it helps.

Dave